US 5,027,926 A · Slip assembly

Abstract

An hydraulically operated slip assembly useful to grip pipe being run into or pulled from a well. This assembly has upper and lower plates, each having a passage for pipe. Wedges, carrying unique slip systems are positioned around the passages between the plates and are slidably mounted for guided radial movement inwardly to initially grip pipe in neutral position and outwardly to ungrip pipe as moved by an hydraulic cylinder pivotally mounted aside on the lower plate. The unique slip systems automatically increase gripping force on initially gripped pipe on more than about 0.7 inches up or down movement from neutral position caused by loads on the pipe. Forces resulting from increased pipe gripping force on pipe develop frictional forces within the slip assembly, which effectively prevent outward movement of the wedges after inadvertent or on purpose operation of the cylinder to ungrip the pipe. The gripped pipe must be moved to return the slip systems to neutral position where the slip systems are not automatically increasing gripping force on pipe before the cylinder can move the slip systems outwardly to ungrip pipe. The slip systems automatically return to neutral position on ungripping pipe.

Claims13

Dependent claims

A slip assembly for gripping pipe comprising:

(a) housing means through which pipe is moved into and out of a well;
(b) means in said housing for gripping pipe including
wedges mounted for radial movement in said housing, a secondary wedge on each wedge, said wedges and secondary wedges each having an opening therethrough,
a slip on each secondary wedge, said slips each having a recess therein, and
means slidably connecting said slips to said secondary wedges and said secondary wedges to said wedges, said slidably connecting means including
pawls swivelably connected into each side of said wedges and slips, each said pawl having a flat surface, and
cam plates connected to each side of said secondary wedge, said cam plates having inner and outer grooves, said flat surfaces on said wedge pawls slidable in said cam plate outer grooves and said flat surfaces on said slip pawls slidable in said cam plate inner grooves;
(c) means for operating said gripping means between positions initially gripping and not gripping pipe;
and
(d) means associated with said pipe gripping means for automatically increasing gripping force on initially gripped pipe in response to subsequent upward or downward longitudinal movement of gripped pipe in excess of about 0.7 inches.

7 more elements

Dependencies are inferred from the claim text.

Slip assembly

Life of this patent

Slip assembly

Life of this patent

Abstract

Claims13